Hi Yuan,



based on what I have learned about thermal cycling tests, it is not the

low temperature that ' kills the part' but the higher delta T of 165K

compared with 125K, an increase of 32%.  To prove this, you can run a

-40C to +85C profile which should have the same result as the 0C to 125C

profile.



             Volkmar



Yuan Li wrote:



>

>

> We have seen some interesting phenomenaduring TCT. We compared 0-125C

> to -40- 125C. For the same package, we had no failures after 2000

> cycles with the 1st profile, but had 1st failure @ 500 cycles with the

> 2nd profile. It appears that the -40 C excursion is what kills the

> part.The most common failure we saw was substrate trace crack. The

> substrate was 2-2-2 build-up BT substrate. I know at -40C Young's

> modulus is higher. Is it a major factor? Any other factors? Why -40C

> would make sucha big difference?

>

> Recall there were some discussions on this topic, however, cannot find

> them. Any papers or on line info available?

>

> Thanks,

>

> Yuan







  Volkmar Huß, C.I.D.



  Engineering Electronic Circuit Boards

  Aufbau- und Verbindungstechnik

  _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _



  DRÄGER ELECTRONICS



  Draeger Electronics GmbH

  Moislinger Allee 53-55

  D-23558 Lübeck



  Tel:   +49-451-882-3998

  Fax: +49-451-882-4365

  mailto:[log in to unmask]

  Website http://www.draeger-electronics.com

  _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _



Important Notice

This email and any attachment hereto are confidential and may contain trade

secrets or may be otherwise protected from disclosure. If you have received

it in error you are in notice of this fact. Please notify us immediately by

reply email and then delete this email and any attachment from your system.

Please understand that you are not allowed to copy this email or any

attachment hereto or disclose its contents to any other person. Thank you.